Vodacom Locking me in a Contract with Poor Service

Been talking with Vodacom about poor connection in my area for ages now. They still insist I stay tied into my contract, even when I advise that I don't have connection. It's not right to be locked into a contract that doesn't provide the service you're paying for. Countless calls and reference numbers suggesting they're attending to the issue, and then a call back saying the issue has been fixed, but the connection remains flat. I've had technicians from Vodacom say the same thing. Is it not possible to end this contract early if I'm battling with your service?